1. Field of the Invention
The invention refers to a process for utilizing of zinc-containing metallurgical dusts and sludges.
2. Description of the Prior Art
The utilization of zinc-containing metallurgical dusts and sludges by using same as secondary raw materials in zinc smelters is not economic in case where zinc contents of these dusts and sludge are below 20 percent by weight. The lack of economy results, on the one hand, from the high costs of hydro-metallurgical processes with subsequent electrolysis and, on the other hand, from the fact that there result great amounts of residual sludges having a high iron content. An economic utilization of such zinc wastes is, at present, possible by means of rotary kiln processes in case of zinc contents of approximately 30 percent by weight.
The utilization of metallurgical dusts and sludges having a low zinc content within the range of 0.1 to 10 percent by weight is presently effected by charging these materials in electric arc furnaces. The enrichment in zinc is effected within the waste gas filters up to a zinc concentration of about 20 percent by weight. When using zinc-containing dusts in converters, there were already made considerations for carrying on the so-called zinc spiral, i.e. the circuit between evaporation and condensation of the zinc within the interior of the converter, to such a degree that it becomes possible to obtain dusts having a zinc content of approximately 20 percent by weight. Such a procedure suffers, however, from the metallurgical drawback that the zinc content within the steel is increased on account of the high reaction temperature, so that, as a whole, the economy is insufficient in case of a utilization in zinc smelters.